Forty percent of those reading this are likely doing so on the go – and that’s why Google is changing its algorithm to favor ‘mobile-friendly’ sites. Business owners are crossing their fingers that the tech giant’s formula won’t negatively impact them.

Sites with text too small to read on a mobile device and those with links too close together are among the reasons why some websites will fall down on the ranking list. Websites that load slowly on mobile devices, as well as those not easily accessed by scrolling up and down, will also take a hit.

Consequently, those sites can expect to see a dramatic reduction in online visitors.

“Some sites are going to be in for a big surprise when they find a drastic change in the amount of people visiting them from mobile devices,” Itai Sadan, CEO of website-building service Duda, told Business Insider.